Heat exchanger

ABSTRACT

A heat exchanger comprises a plurality of flow pipes for a first fluid and an envelope delimiting an internal volume in which the pipes are placed. The envelope has an inlet for a second fluid and an outlet for the second fluid opening into the internal volume. At least one internal grid is arranged between the inlet of the second fluid and the outlet of the second fluid. The internal grid divides the internal volume into a plurality of chambers arranged one after another in a longitudinal direction. The internal grid delimits a passage for the second fluid with an internal surface of the envelope, wherein the or each passage is arranged such that the second fluid circulates in a labyrinthine fashion from the inlet of the second fluid to the outlet of the second fluid via the chambers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. non-provisional application claiming the benefit of French Application No. 19 01610, filed on Feb. 18, 2019, which is incorporated herein by its entirety.

TECHNICAL FIELD

In general, the invention concerns heat exchangers, in particular heat exchangers for vehicle exhaust lines.

BACKGROUND

It is possible to install a heat exchanger on board a vehicle with a combustion engine in order to recover the thermal energy of the exhaust gas.

Such a heat exchanger may include pipes in which the exhaust gas circulates, these pipes being arranged within an envelope inside which a fluid, typically a coolant, circulates.

The temperature of the exhaust gas is high, typically several hundred ° C. when the engine is operating at a full load, upon entering the pipes.

As such, there is a risk that the coolant will be brought to a boil when it circulates in contact with the upstream portion of the pipes. If it boils, an increase in temperature of the heat exchanger will be observed, because the coolant, having been vaporized, is no longer cooling the heat exchanger. The increase in temperature of the wall of the heat exchanger will generate increased thermal constraints, up to and including breakage of the heat exchanger, and cause considerable degradation of the coolant. To limit this risk, the circulation of the coolant must be properly controlled.

In this context, a heat exchanger is proposed in which the circulation of the coolant is properly controlled.

SUMMARY

In one exemplary embodiment, a heat exchanger includes

a plurality of flow pipes for a first fluid;

an envelope delimiting an internal volume, in which the pipes are placed, wherein the envelope has an inlet for a second fluid and an outlet for a second fluid opening into the internal volume, wherein the inlet for the second fluid and the outlet for the second fluid are longitudinally offset from one another;

at least one internal grid arranged within the internal volume, longitudinally between the inlet of the second fluid and the outlet of the second fluid and dividing the internal volume into a plurality of chambers arranged one after another in the longitudinal direction, wherein the or each internal grid has orifices in which the pipes engage, wherein the or each internal grid has an external peripheral edge, one section of which delimits a passage for the second fluid with an internal surface of the envelope, wherein the or each passage is arranged such that the second fluid circulates in a labyrinthine fashion from the inlet of the second fluid up to the outlet of the second fluid via the chambers.

Thus, the internal grid(s) is/are arranged so as to force the second fluid to circulate in a labyrinthine manner from the inlet to the outlet of the pipes of the heat exchanger. The second fluid will thus successively sweep each chamber.

When the first fluid is an exhaust gas of a vehicle and the pipes are arranged such that the upstream part of the pipes traverses the first chamber, into which the inlet of the second fluid opens, the upstream part of the pipes is particularly well cooled. The internal grid forces the second fluid to circulate in contact with the upstream part of the pipes.

The heat exchanger may additionally have one or more of the following features, taken individually or in any combination technically possible:

for the or each internal grid, the envelope has an area raised towards the outside delimiting the passage with the section of the internal grid;

in the or each internal grid, openings are arranged between each pipe and an inner edge of the corresponding orifice;

the pipes each have an elongated cross section in the transverse direction and are superimposed in a direction of elevation, wherein the inner edges of the orifices carry transverse strips that abut the pipes in the direction of elevation;

the inner edge of each orifice has two transverse edge sections arranged opposite one another, wherein each transverse edge section carries several strips that are spaced transversely apart from one another;

the orifices of a single internal grid are separated by transverse full bands of the internal grid, wherein the transverse full bands each define two transverse edge sections of the orifice, wherein the strips of the two transverse edge sections are staggered;

the strips are inclined towards the inside of the orifice;

the peripheral edge of the or each internal grid has first and second full bands extending on either side of the orifices in the transverse direction, wherein the first full band defines the section of the outer peripheral edge and has a smaller width in the transverse direction than that of the second full band;

the exchanger comprises several internal grids, all of which are identical, wherein two consecutive internal grids are orientated inversely in the longitudinal direction, such that the first full bands of the two grids are turned inversely in the transverse direction;

the internal grid nearest to the outlet of the second fluid is orientated with the second full band turned towards the outlet of the second fluid, wherein the envelope has at least one intermediate area that is raised towards the outside opposite an intermediate section of the outer peripheral edge arranged between the first full band and the second full band.

the outer peripheral edge of the or each internal grid carries external strips abutting the inner surface of the envelope.

In a second aspect, the disclosure concerns an exhaust line including a heat exchanger having the aforementioned features, wherein the first fluid is the exhaust gas and the second fluid is a coolant provided in order to recover part of the thermal energy of the exhaust gas.

Preferably, the pipes are straight longitudinal pipes, with the first fluid flowing from the upstream end of the pipes to the downstream end of the pipes, the inlet for the second fluid being arranged opposite the upstream end of the pipes, and the outlet for the second fluid being arranged opposite the downstream end of the pipes.

The inlet for the second fluid opens into an upstream chamber that is traversed by the upstream ends of the pipes.

The outlet for the second fluid opens into a downstream chamber that is traversed by the downstream ends of the pipes.

The upstream and downstream chambers are arranged at two opposite longitudinal ends of the series of chambers.

In a third aspect, the disclosure concerns a vehicle including an exhaust line having the aforementioned features.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the disclosure will be seen from the following detailed description, provided by way of example only, which refers to the attached drawings, which show:

FIG. 1 is a perspective view of a heat exchanger according an exemplary embodiment;

FIG. 2 is a longitudinal cutaway view of the heat exchanger of FIG. 1, viewed along the arrows II;

FIG. 3 is a cutaway view of the heat exchanger of FIG. 1, viewed along the arrows III;

FIG. 4 is an exploded perspective view of the pipes and internal grids of the heat exchanger of FIG. 1;

FIG. 5 is an enlargement of part of an internal grid of FIG. 4;

FIG. 6 is an enlarged cutaway view of a detail VI of FIG. 3; and

FIG. 7 is a transverse cutaway view of the heat exchanger, viewed along the arrows VII of FIG. 2.

DETAILED DESCRIPTION

The heat exchanger 1 shown in FIG. 1 is typically intended for incorporation into a vehicle exhaust line. The vehicle is a vehicle with a combustion engine, e.g., a car, lorry, or a two-wheeled vehicle.

The heat exchanger 1 comprises:

a plurality of flow pipes 3 for a first fluid;

an envelope 5 delimiting an internal volume 6 in which the pipes 3 are arranged,

wherein the envelope 5 has an inlet 7 for a second fluid and an outlet 9 for a second fluid that opens into the internal volume 6.

Typically, the first fluid is the exhaust gas of the vehicle.

The second fluid is typically a coolant provided in order to recover part of the thermal energy of the exhaust gas.

Typically, the pipes 3 are straight, longitudinal pipes. The longitudinal direction is indicated in the figures by the arrow L.

As can be seen in FIGS. 1-4, the pipes 3 each have an elongated cross section in the transverse direction and are superimposed in a direction of elevation.

The transverse direction is indicated in the figures by an arrow T. The direction of elevation is indicated in the figures by an arrow E.

‘Cross section’ refers to a section perpendicular to the longitudinal direction L.

In the example shown, the pipes 3 have a ‘racetrack’ cross section.

Each pipe 3 has a constant cross section, i.e. it is identical no matter what slice plane is considered when followed longitudinally.

Thus, each pipe 3 is delimited by first and second large surfaces 11, 13 arranged opposite one another and connected by arched sections 15, 17 that are arranged opposite one another. The first and second large surfaces 11, 13 are perpendicular to the direction of elevation E. Thus, they each extend along planes that are substantially longitudinal and transverse. The second large surface 13 of a pipe 3 is arranged above and opposite the first large surface 11 of the pipe 3 arranged immediately below it in the stack.

The arched sections 15 and 17 are turned transversely in opposite directions.

In the example shown, the pipes 3 are arranged so as to form a single stack in the direction of elevation E. In other words, in the transverse direction T, the heat exchanger 1 includes only one pipe 3, which occupies substantially the entire transverse width of the heat exchanger 1. In this description, the stack will also be referred to as a pipe bundle.

Each pipe 3 delimits an inlet 19 for a first fluid at one longitudinal end and an outlet 21 for the first fluid at the opposite longitudinal end. A metal foil 23 folded so as to form fins is inserted into each pipe 3.

The envelope 5 is tubular in shape, having a central axis that is substantially longitudinal. It has substantially rectangular cross sections, with four large surfaces 24 that are generally flat and connected to one another via rounded portions.

At its two longitudinal ends, the envelope 5 delimits upstream and downstream openings 25, 27 in which end grids 29 engage. In this description, the terms ‘upstream’ and ‘downstream’ are understood relative to the direction of flow of the first fluid.

The end grids 29 have orifices 31 for receiving longitudinal ends of the pipes 3. These longitudinal ends are affixed in a gas-tight manner within the orifices 31 and traverse the end grids 29.

Thus, the pipes 3 extend longitudinally over the entire length of the envelope 5.

The inlet 7 of the second fluid and the outlet 9 of the second fluid are longitudinally offset from one another.

The inlet 7 is located longitudinally near the upstream opening 25, and the outlet 9 is near the downstream opening 27.

In the example shown, the inlet 7 of the second fluid and the outlet 9 of the second fluid are slots cut in the envelope 5. These slots are elongated in the direction of elevation E, and have a height substantially equal to the height of the stack of pipes 3.

Advantageously, the heat exchanger 1 comprises at least one internal grid 33 arranged within the internal volume 6, longitudinally between the inlet 7 of the second fluid and the outlet 9 of the second fluid.

It divides the internal volume 6 into a plurality of chambers arranged one after another in the longitudinal direction.

The heat exchanger 1 includes an internal grid 33, or two internal grids 33, or three internal grids 33 as in the example shown in the drawings, or any other number of internal grids 33, depending on the longitudinal length of the heat exchanger 1.

The or each internal grid 33 typically extends perpendicularly to the longitudinal direction L.

The internal volume 6 includes at least one upstream chamber 35, into which the inlet 7 of the second fluid opens, and a downstream chamber 37, into which the outlet 9 of the second fluid opens.

It may optionally comprise one or more intermediate chambers 39 located longitudinally between the chambers 35 and 37.

Each chamber 35, 37, 39 extends transversely over the entire section of the internal volume 6. Each chamber 35, 37, 39 thus occupies a longitudinal section of the internal volume 6.

The upstream chamber 35 is delimited between the end grid 29 engaged in the upstream opening 25 of the envelope 5 and the internal grid 33 arranged most upstream. The downstream chamber 37 is delimited between the end grid 29 engaged in the downstream opening 27 of the envelope 5 and the internal grid 33 arranged most downstream.

The or each intermediate chamber 39 is delimited between two internal grids 33.

As can be seen in FIG. 4, the or each internal grid 33 has orifices 41 in which the pipes 3 engage. The internal grid 33 has an orifice 41 for each pipe 3.

Each orifice 41 has a closed contour. It has an internal section close to the outer transverse section of the corresponding pipe 3.

In the example shown, the orifices 41 of the or each internal grid 33 are all elongated in the transverse direction. They are superimposed in the direction of elevation E. They are all identical.

In one example, which can be seen, in particular, in FIG. 2, the or each internal grid 33 has an outer peripheral edge 42 (FIG. 4), one section 43 of which delimits a passage 45 for the second fluid with an internal surface of the envelope 5. The or each passage 45 is arranged such that the second fluid circulates in a labyrinthine fashion from the inlet 7 of the second fluid to the outlet 9 of the second fluid via the chambers 35, 39, 37.

‘Circulation in a labyrinthine manner’ refers here to the fact that the second fluid circulates from the inlet 7 over a course comprising a series of 180° U-turns, with the successive U-turns defining slots.

In other words, the passages 45 are arranged such that the second fluid, starting from the inlet 7 of the second fluid, traverses the upstream chamber 35 in the transverse direction, then executes a U-turn, traversing the passage 45 to pass into the upstream chamber 35 of the subsequent chamber.

The second fluid then traverses the next chamber in the transverse direction, then arriving at the outlet 9 of the second fluid, or, if the heat exchanger includes more than two chambers, executes another 180° change in direction to pass into the next chamber, etc. until the outlet 9 of the second fluid.

In the example shown, the or each internal grid 33 is substantially rectangular, and the section 34 extends over an entire side of the internal grid 33. The rest of the outer peripheral edge 42 abuts the inner surface of the envelope 5 so as to prevent the passage of the second fluid.

To this end, the outer peripheral edge 42 of the or each internal grid 33 has external strips 47 (FIGS. 4 and 5) abutting the inner surface of the envelope 5 (FIG. 6).

In the example shown, the or each internal grid 33 includes an outer strip 47 on each side.

The outer strip 47 is folded so as to form an angle slightly greater than 90° relative to the plane on which the orifices 41 through which the pipes 3 pass are formed. At the level of its corners, the outer peripheral edge 42 has no folded strip, but does have a non-folded strip 49 on the plane of the orifices 41 for the passage of the pipes 3. The free edge of the non-folded strip 49 adapts to the inner surface of the envelope 5, creating a tight seal against the second fluid.

The outer strip 47 carried by the section 43 does not abut the inner surface of the envelope 5. On the other hand, the outer strips 47 carried by the other portions of the outer peripheral edge do abut the inner surface of the envelope 5.

Additionally, in the or each internal grid 33, openings 51 are provided between each pipe 3 and the inner edge 53 of the corresponding orifice 41 (FIG. 7).

As can be seen in the drawings, the inner edges 53 of the orifices 41 carry transverse strips 55 that abut the pipes 3 in the direction of elevation E (FIGS. 4-6).

More specifically, the inner edge 53 of each orifice 41 has two transverse edge sections 57 arranged opposite one another. The transverse edge sections 57 are connected to one another via terminal edge sections 59.

Each transverse edge section 57 carries several strips 55, spaced apart from one another in the transverse direction.

The strips 55 are inclined towards the inside of the orifice 41, as shown in FIG. 6. Relative to the longitudinal direction L, they form an angle 13 between 2 and 6°, typically equal to 4°.

The strips 55 are all inclined in the same manner

As can be seen, in particular, in FIGS. 4 and 5, the orifices 41 of a single internal grid 33 are separated from one another by transverse full bands 61 of the internal grid 33.

Each transverse full band 61 defines the transverse edge section 57 of the orifice 41 arranged immediately below and the transverse edge section 57 of the orifice 41 arranged immediately above.

The strips 55 of these two transverse edge sections 57 are staggered, as can be seen more clearly in FIG. 5.

This means that the strips 55 carried by one of the two transverse edge sections 57 are separated by spaces 63. The strips 55 of the other transverse edge section 57 are arranged opposite the spaces 63.

The openings 51 correspond here to the intervals 63 between the strips 55.

Advantageously, the sum of the transverse lengths of the strips 55 is equal to half the transverse width of the tube 3.

The clearance angle β allows for the maintenance of the distance between the various pipes 3, and for the centering of the bundle of pipes 3 within the envelope 5 of the heat exchanger 1 in the direction of elevation E.

To this end, in the resting state, the free edges of the strips 55 on either side of a single orifice 41 are separated in the direction of elevation E by a distance smaller than the width of the pipe 3. The thickness is taken along the direction of elevation E.

When the pipes 3 are inserted into the orifices 41, the strips 55 are elastically deflected in order to allow the tube 3 to pass without any play.

Likewise, the outer strips 47 allow the internal grids 33 to engage in the envelope 5 by elastic flexion of the outer strips 47. The clearance angle of the outer strips 47 may be greater than that of the strips 55 in order to guarantee potentially greater tolerances.

For the or each internal grid 33, the envelope 5 has an area raised towards the outside delimiting the passage 45 with the section 43 of the internal grid 33. The elevated area 65 is hollow in the direction of the inside of the envelope 5. It is arranged transversely opposite the section 43. It extends over the majority of the transverse width of the envelope 5.

Thus, it is possible to increase the free flow area available to the second fluid through the passage 45. This reduces back pressure.

Advantageously, the internal grids 33 are all identical.

The outer peripheral edge 42 of the internal grid 33 has first and second full bands 67, 69 extending on either side of the orifices 41 in the transverse direction T.

The first full band 67 is elongated in the direction of elevation E. It adjoins the terminal edge sections 59 of the orifices 41. It is located on a first transverse end of the orifices 41.

The second full band 69 also extends in the direction of elevation E. It adjoins the terminal edge sections 59 opposite the orifices 41. It is located on the other transverse side of the orifices 41.

The first full band 67 defines the section 43 of the outer peripheral edge 42, and has a width 11 in the transverse direction. The second full band 69 has a width 12 in the transverse direction. The transverse width 11 is smaller than the transverse width 12.

Additionally, the inner grids 33 are arranged such that two consecutive inner grids 33 in the longitudinal direction L have inverse orientations. The full bands 67 of the two internal grids 33 are turned inversely in the transverse direction T.

Thus, the passages 45 delimited by two consecutive internal grids 33 are arranged transversely on two opposite sides of the heat exchanger 1, which makes the labyrinthine circulation possible.

The corresponding elevated areas 65 are also arranged on two transversely opposite sides of the heat exchanger 1.

The internal grid 33 nearest the inlet 7 of the second fluid is orientated such that the first full band 67 is arranged transversely opposite the inlet 7 of the second fluid. Thus, the passage 45 from the upstream chamber 35 to the chamber immediately downstream is arranged transversely opposite the inlet 7 of the second fluid. The second fluid is forced to traverse the entire upstream chamber 35 starting from the inlet 7 of the second fluid, in order to arrive at the passage 45.

The internal grid 33 nearest the outlet 9 of the second fluid is orientated with the first full band 67 turned transversely opposite the outlet 9 of the second fluid. Thus, the passage 45 by which the downstream chamber 37 can be accessed is arranged transversely opposite the outlet 9 of the second fluid. The second fluid penetrating into the downstream chamber 37 via the passage 45 is forced to traverse the entire downstream chamber 37 transversely in order to arrive at the outlet 9 of the second fluid.

When the heat exchanger 1 includes several internal grids 33, the envelope 5 has a specific shape at the level of the internal grid 33 nearest the outlet 9 of the second fluid. More specifically, it has an intermediate area 71 that is elevated towards the outside, opposite an intermediate section 73 of the outer peripheral edge 42 that is arranged between the first full band 67 and the second full band 69.

Preferably, the envelope 5 includes two intermediate areas 71 that are elevated towards the outside, arranged on two opposite sides of the envelope 5 in the direction of elevation E.

In the example shown, the intermediate sections 73 of the outer peripheral edge 42 are the sides of the internal grid 33 with a transverse orientation. These sides connect the first and second full bands 67, 69 to one another. One of the intermediate sections 73 is arranged above the stack of pipes 3, and the other is arranged below it.

The or each intermediate elevated area 71 typically extends transversely over substantially the entire width of the envelope 5.

Thus, bypasses 75 are created for the second fluid between the or each intermediate section 73 and the or each intermediate elevated area 71.

In other words, the second fluid may flow up to the downstream chamber 37 simultaneously via the passage 45 and the bypasses 75.

These bypasses 75 allow for a reduction of back pressure above and below the stack of pipes 3.

The internal grids 33 are typically formed from a thin metal sheet having a thickness between 0.2 and 0.8 mm, typically having a thickness of 0.4 mm.

Preferably, they are obtained by cutting and folding the thin metal sheet. These operations allow for the formation of the orifices 41 for the passage of the pipes 3, and the strips 47 and 55, as well as the non-folded strips 49.

The operation of the heat exchanger 1 shown in the drawings will now be described.

The first fluid flows within the pipes 3. It enters each pipe 3 by the upstream end 19 thereof, leaving via the downstream end 21.

The first fluid is cooled in the heat exchanger 1 such that it has a higher temperature at the upstream 19 end than at the downstream end 21.

The second fluid penetrates into the internal volume 6 via the inlet 7 for the second fluid. Due to the presence of the internal grid 33 in the most upstream position, it is forced to flow transversely between the pipes 3. Thus, it traverses the upstream chamber 35 in the transverse direction up to the passage 45. At the level of the passage 45, it follows a U-shaped course and, having penetrated into the first intermediate chamber 39, it flows transversely in the opposite direction. It again flows transversely over the entire width of the intermediate chamber 39 up to the passage 45 that is arranged at the opposite transverse end of the intermediate chamber 39.

Due to its inertia, the second fluid that penetrates the intermediate chamber 39 by the passage 45 is carried off towards the second internal grid 33. On the other hand, some of the second fluid flows from the upstream chamber 35 to the first intermediate chamber 39 via the openings 51. Thus, the area of the first intermediate chamber 39 that is arranged immediately along the most upstream internal grid 33 is swept by the second fluid coming from the openings 51.

The second fluid passes from the first intermediate chamber 39 to the second intermediate chamber 39 via the passage 45 that is arranged transversely on one side of the inlet 7 of the second fluid and the outlet 9 of the second fluid and via the openings 51 of the second internal grid 33.

The second fluid passes from the second intermediate chamber 39 to the downstream chamber 37 both via the passage 45 delimited by the third internal grid 33 and the bypasses 75. It also passes through the openings 51 of the third internal grid 33.

The second fluid leaves the downstream chamber 37 via the outlet 9 of the second fluid.

The invention has multiple advantages.

Because the second fluid flows in a labyrinthine manner from the inlet 7 of the second fluid to the outlet 9 of the second fluid via the chambers 35, 39, 37, the part of the pipes arranged within the upstream chamber 35 is swept particularly well by the second fluid.

When the first fluid is very hot, this ensures excellent cooling of the first fluid without any risk of the second fluid boiling.

The fact that the envelope has areas elevated towards the outside in order to delimit the passage that connects one chamber to another allows for easy adjustment of the volume of liquid passing through the passage. This adjustment is carried out by selecting the depth of the elevated area.

The existence of openings arranged between each pipe and the inner edge of the corresponding orifice in the internal grid allows for sweeping of the area of the internal volume immediately upstream the internal grid with a sufficient flow of the second fluid.

The transverse strips carried by the inner edges of the orifices allow the distance between the pipes in the direction of elevation to be controlled. Thus, no protuberances by which the pipes abut one another are provided in the pipes. Such protuberances are traditionally used to control the height of the space between the pipes. They have the disadvantage that there is no contact between the fins and the wall of the pipe at the level of the protuberances, which locally interrupts the heat flow from the fins to the pipe.

The fact that the strips are spaced apart transversely from one another allows openings to be conveniently created between each pipe and the inner edge of the corresponding orifice.

The amount of the second fluid that passes through the openings can thus easily be controlled by modulating the spacing between the strips in the transverse direction.

The fact that the strips carried by a single transverse full band are staggered allows for the creation of a more complex fluid pathway for the second fluid that passes through the openings. This reduces the flow passing between the pipes and the edge of the corresponding orifice.

Because the strips are inclined towards the inside of the orifice, the pipe bundle can be centered within the body of the heat exchanger in the direction of elevation, and the space between the pipes can be maintained in the direction of elevation. This also makes the insertion of the pipes into the orifices quite convenient.

The fact that first and second full bands with different transverse widths are provided on either side of the orifices makes it possible to provide for labyrinthine flow using identical grids.

To this end, consecutive grids are turned in opposite directions.

This additionally means that the bundle of pipes is conveniently centered transversely relative to the envelope.

The risk that the second fluid may boil exists essentially in the chamber into which the inlet of the second fluid opens, and, in some cases, in the chamber arranged immediately downstream. The risk is considered practically nil in the most downstream chamber, into which the outlet of the second fluid opens.

As such, it is advantageous to provide at least one intermediate area that is elevated towards the outside within the envelope at a right angle to the internal grid nearest the outlet.

As noted above, this allows for bypasses to be created around the internal grid, which reduces back pressure above and below the pipe bundle. In particular, this allows for increases in the flow rate of the second fluid in the parts of the chambers above and below the pipe bundle. As described above, the inlet for the second fluid has a height in the direction of elevation that is substantially equal to that of the pipe bundle. Its upper end reaches the level of the upper pipe, and its lower end reaches that of the lower pipe. It is not possible to extend the fin any further because the envelope is bowed between its lateral surfaces and its upper/lower surfaces.

The volumes of the upstream chamber arranged above and below the pipe bundle have less contact with the second fluid that penetrates the inlet than the volumes arranged between the pipes. The elevated intermediate area(s) allow(s) for an increase in the flow rate of the second fluid in these underserved volumes of the downstream chamber.

Multiple variants of the heat exchanger described above are possible.

The disclosed example has been described with straight pipes extending longitudinally over the entire length of the heat exchanger and passing, in this order, through the upstream chamber, any intermediate chambers, and the downstream chamber.

The pipes may be in any other shape or arrangement. The pipes may, e.g., be U-shaped, with two longitudinal portions connected by an arch.

It was described above that the or each internal grid has outer strips 47 that are separated from one another. In one variant, the or each internal grid has a single strip extending circumferentially along the entire outer peripheral edge 42.

In this case, the grid is produced by stamping.

Alternatively, the or each internal grid is produced from a thicker metal plate. The orifices 41 for receiving the pipes are cut off. The grid has no outer strip 47 or strip 55 to separate the pipes. The openings 51 are produced by removing metal or by deformation.

The width of the transverse strips 55 is not necessarily constant. The strips 55 may have a variable width in the transverse direction along a single orifice. The width of the strips 55 may also vary from one grid to another.

It was described above that all of the internal grids are identical in order to optimize manufacturing costs. In one variant, the internal grids are different to one another, thus allowing for adaptations of the fluid behavior of the heat exchanger.

In the example described, the grids are rectangular. In one variant, they are ovals, in ‘racetrack’ configuration, or in any other suitable form.

In this case, the envelope has a cross section corresponding to the shape of the grid.

In the example shown, the heat exchanger includes only one pipe in the transverse direction. In one variant, it includes several pipes that are juxtaposed in the transverse direction.

In one variant, the heat exchanger is not provided for incorporation into the exhaust line of a vehicle. It may be incorporated into any other circuit of the vehicle, or even any other type of equipment.

The first fluid is not necessarily the exhaust gas of the vehicle; it may be of any other type. The first fluid is a gas or liquid, and may be of any type.

Likewise, the second fluid is not necessarily a coolant. The second fluid is a gas or a liquid of any kind.

Although various embodiments have been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this disclosure. For that reason, the following claims should be studied to determine the true scope and content of this disclosure. 

1. A heat exchanger, comprising: a plurality of flow pipes for a first fluid; an envelope delimiting an internal volume, in which the plurality of flow pipes are placed, wherein the envelope has an inlet for a second fluid and an outlet for the second fluid opening into the internal volume, wherein the inlet) for the second fluid and the outlet for the second fluid are longitudinally offset from one another; at least one internal grid arranged within the internal volume, longitudinally between the inlet of the second fluid and the outlet (9) of the second fluid and dividing the internal volume into a plurality of chambers, arranged one after another in a longitudinal direction, wherein the or each internal grid has orifices in which the pipes engage, wherein the at least one or each internal grid has an external peripheral edge, one section of which delimits a passage for the second fluid with an internal surface of the envelope, wherein the or each passage is arranged such that the second fluid circulates in a labyrinthine fashion from the inlet of the second fluid up to the outlet of the second fluid via the plurality of chambers.
 2. The heat exchanger according to claim 1, wherein, for the or each internal grid, the envelope has an area raised towards the outside that delimits the passage from the section of the internal grid.
 3. The heat exchanger according to claim 1, wherein, in the at least one or each internal grid, openings are provided between each pipe of the plurality of flow pipes and an internal edge of a corresponding orifice the at least one or each internal grid.
 4. The heat exchanger according to claim 1, wherein the plurality of flow pipes each have a transversely elongated cross section and are superimposed in a direction of elevation, wherein internal edges of the orifices carry transverse strips that abut the plurality of flow pipes in the direction of elevation.
 5. The heat exchanger according to claim 4, wherein the internal edge of each orifice has two transverse edge sections arranged opposite one another, wherein each transverse edge section carries several transverse strips that are spaced transversely apart from one another.
 6. The heat exchanger according to claim 5, wherein the orifices of a single internal grid of the at least one internal grid are separated by full transverse bands of the single internal grid, wherein the full transverse bands each define two transverse edge sections of the orifice, wherein the transverse strips of the two transverse edge sections are staggered.
 7. The heat exchanger according to claim 4, wherein the transverse strips are inclined towards an inside of the orifice.
 8. The heat exchanger according to claim 4, wherein the outer peripheral edge of the or each internal grid has first and second full bands that extend on either side of the orifices in a transverse direction, wherein the first full band defines the section of the outer peripheral edge and has a width in the transverse direction that is smaller than that of the second full band.
 9. The heat exchanger according to claim 8, wherein the at least one or each internal grid comprises several internal grids that are all identical, wherein two consecutive internal grids are orientated inversely in the longitudinal direction such that the first full bands of the two internal grids are inversely turned in the transverse direction.
 10. The heat exchanger according to claim 9, wherein the internal grid nearest to the outlet of the second fluid is orientated with the second full band turned towards the outlet of the second fluid, wherein the envelope has at least one intermediate area that is raised towards the outside opposite an intermediate section of the outer peripheral edge arranged between the first full band and the second full band.
 11. The heat exchanger according to claim 1, wherein the outer peripheral edge of the at least one or each internal grid carries external strips that abut the internal surface of the envelope.
 12. An exhaust line including the heat exchanger according to claim 1, wherein the first fluid is exhaust gas and the second fluid is a coolant provided in order to recover part of thermal energy of the exhaust gas.
 13. A vehicle including the exhaust line according to claim
 12. 